Conventionally, as a gland packing material which is useful in production of a gland packing, for example, known are a material disclosed in Japanese Patent Publication No. 6-27546 (hereinafter, referred to as conventional art 1), and that disclosed in Japanese Patent No. 2,583,176 (hereinafter, referred to as conventional art 2).
In conventional art 1 above, as shown in FIG. 35, for example, tape-like expanded graphite (51) is folded along longitudinal fold lines to form a cord-like member (52), and the cord-like member (52) is covered by a reinforcing member (53) configured by a knitted or braided member of metal wires such as stainless steel, inconel, or monel, thereby forming a gland packing material (50).
In conventional art 2 above, as shown in FIG. 36, for example, a cord-like member (52) of tape-like expanded graphite (51) is covered by a reinforcing member (53) configured by a knitted or braided member of metal wires, and the resulting member is folded to a V-like shape along a longitudinal fold line, thereby forming a gland packing material (50).
In both the gland packing materials (50) of the conventional art, the outside of the cord-like member (52) is reinforced by the reinforcing member (53) configured by a knitted or braided member of metal wires (hereinafter, such reinforcement is referred to as external reinforcement) Therefore, the gland packing materials (50) are provided with high tensile strength. Consequently, a plurality of such gland packing materials (50) are bundled, and then subjected to a braiding or twisting process, so that a gland packing can be produced. In conventional art 1 above, when eight gland packing materials (50) are bundled and an eight-strand square-knitting process is conducted, for example, a gland packing (54) which is braided as shown in FIG. 37 is produced, and, when six gland packing materials (50) are bundled and a twisting process is conducted, a gland packing (54) which is twisted as shown in FIG. 38 is produced. In conventional art 2 above, when eight gland packing materials (50) are bundled and an eight-strand square-knitting process is conducted, for example, a gland packing (54) which is braided as shown in FIG. 39 is produced, and, when six gland packing materials (50) are bundled and a twisting process is conducted, a gland packing (54) which is twisted as shown in FIG. 40 is produced.
Each of the conventional gland packings (54) is provided by the expanded graphite (51) with properties which are preferable in sealing, and which are inevitable in a packing, such as the heat resistance, the compressibility, and the recovery property, and hence can seal a shaft seal part of a fluid apparatus while producing a high sealing property.
On the other hand, as a further gland packing material which is useful in production of a gland packing, for example, known is a material disclosed in Japanese Patent No. 3,101,916 (hereinafter, referred to as conventional art 3).
In conventional art 3, as shown in FIG. 41, for example, both faces of a reinforcing member (53) configured by plural carbon fibers are covered by expanded graphite (51), thereby forming a gland packing material (50) in which the interior is reinforced (hereinafter, such reinforcement is referred to as internal reinforcement).
The gland packing material (50) is provided with high tensile strength by the reinforcing member (53) configured by the carbon fibers, and hence can be subjected to a braiding or twisting process. When a plurality of such gland packing materials (50) are bundled, and then a braiding or twisting process is applied to the bundle, therefore, a gland packing can be produced. When eight gland packing materials (50) are bundled and an eight-strand square-knitting process is conducted, for example, a gland packing (54) which is braided as shown in FIG. 37 is produced, and, when six gland packing materials (50) are bundled and a twisting process is applied, a gland packing (54) which is twisted as shown in FIG. 38 is produced.
Each of the conventional gland packings (54) is provided by the expanded graphite (51) with properties which are preferable in sealing, and which are inevitable in a packing, such as the compressibility and the recovery property, and hence can seal a shaft seal part of a fluid apparatus while producing a high sealing property.
In the gland packing material (50) having the external reinforcement structure disclosed in conventional art 1 or 2, however, the cord-like member (52) of the expanded graphite (51) is covered by the reinforcing member (53). Therefore, the gland packing material can obtain an excellent shape-retaining property, but has a drawback that the sealing property is poor. By contrast, in the gland packing material (50) having the internal reinforcement structure disclosed in conventional art 3, the surface of the reinforcing member (53) is covered by the expanded graphite (51). Therefore, the gland packing material can obtain an excellent sealing property, but has a drawback that the shape-retaining property is poor. In the gland packing (54) which is produced by bundling a plurality of the gland packing materials (50) having the poor sealing property and then applying a braiding or twisting process to the bundle, it is not expected to exert a high sealing property. In the gland packing (54) which is produced by bundling a plurality of gland packing materials (50) having the poor shape-retaining property and then applying a braiding or twisting process to the bundle, there is a possibility that the expanded graphite (51) drops off during the braiding or the twisting process, the elasticity of the gland packing (54) is reduced, the properties which are preferable in sealing, such as the compressibility and the recovery property are lost, and the sealing property of the gland packing (54) is lowered.
The invention has been developed in view of the above-described circumstances. It is an object of the invention to provide a gland packing material which is provided with high tensile strength by a reinforcing member to be easily subjected to a braiding or twisting process, and which has both an excellent shape-retaining property that is possessed by a gland packing material having the external reinforcement structure, and an excellent sealing property that is possessed by a gland packing material having the internal reinforcement structure, and a gland packing which is produced with using the gland packing material.